 The visual band light curve of HD 137509, adapted from Lanz & Mathys (1991) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Apus |
| Right ascension | 15 31 27.11494 |
| Declination | −71° 03′ 43.6643″ |
| Apparent magnitude (V) | 6.89 |
| Characteristics | |
| Spectral type | B9p (SiCrFe) B8 He wk SiCrFe |
| B−V color index | −0.125±0.004 |
| Variable type | α CVn |
| Astrometry | |
| Radial velocity (Rv) | +0.50 km/s |
| Proper motion (μ) | RA: −16.276 mas/yr Dec.: −15.503 mas/yr |
| Parallax (π) | 5.0410 ± 0.0503 mas |
| Distance | 647 ± 6 ly (198 ± 2 pc) |
| Absolute magnitude (MV) | 0.45 |
| Details | |
| Mass | 3.43±0.17 M☉ |
| Radius | 2.81 R☉ |
| Luminosity | 123 L☉ |
| Surface gravity (log g) | 4.3 cgs |
| Temperature | 13,100±500 K |
| Rotation | 4.492 d |
| Rotational velocity (v sin i) | 20±2 km/s |
| Age | 124 Myr |
| Other designations | |
| NN Aps, CD−70°1302, GC 20810, HD 137509, HIP 76011, SAO 257290 | |
| Database references | |
| SIMBAD | data |
HD 137509 is a star in the southern constellation of Apus, positioned less than a degree from the northern constellation boundary with Triangulum Australe. It has the variable star designation of NN Apodis, or NN Aps for short, and ranges in brightness from an apparent visual magnitude of 6.86 down to 6.93 with a period of 4.4916 days. The star is located at a distance of approximately 647 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +0.50 km/s.
In 1973, W. P. Bidelman and D. J. MacConnell found this to be a peculiar A star of the silicon type. During a reclassification of the spectra of southern stars in 1975, A. P. Cowley and N. Houk noted the strength of hydrogen lines and weakness of helium are more typical of a class near B9. It shows a luminosity above the main sequence, which is common for a peculiar A star. The stellar atmosphere appears deficient in helium, but shows a rich variety of metallic lines. However, there are no lines of manganese or mercury, so it's not a Hg–Mn Ap star. HD 137509 is now classified as B9p (SiCrFe) or B8 He wk SiCrFe, matching a late-type, helium-weak Bp star with overabundances of silicon, chromium, and iron.
This star was found to be photometrically variable by L. O. Lodén and A. Sundman in 1989, and a variable spectrum was noted by H. Pedersen in 1979. It has one of the strongest magnetic fields recorded for a chemically peculiar star, measured at around 29 kG, and shows a strong quadrupolar component. Both variances of the star allow its rotation period to be precisely measured. It is classified as a Alpha Canum Venaticorum variable. The star is about 124 million years old with 3.4 times the mass of the Sun and 2.8 times the Sun's radius. On average it is radiating ~123 times the luminosity of the Sun from its photosphere at an effective temperature of 13,100 K.
References
- Lanz, T.; Mathys, G. (August 1991). "The Photometric Variability of the B9p Star HD 137509". Information Bulletin on Variable Stars. 3655: 1. Bibcode:1991IBVS.3655....1L.
- ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
- ^ Shulyak, D.; et al. (2008). "Model atmospheres of magnetic chemically peculiar stars. A remarkable strong-field Bp SiCrFe star HD 137509". Astronomy and Astrophysics. 487 (2): 689–96. arXiv:0806.1296. Bibcode:2008A&A...487..689S. doi:10.1051/0004-6361:20079134. S2CID 14113957.
- ^ Bailey, J. D.; Landstreet, J. D. (2013). "Abundances determined using Si ii and Si iii in B-type stars: Evidence for stratification". Astronomy & Astrophysics. 551: A30. arXiv:1301.3050. Bibcode:2013A&A...551A..30B. doi:10.1051/0004-6361/201220671. S2CID 59291051.
- ^ Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
- ^ Barbier-Brossat, M.; Petit, M.; Figon, P. (December 1994). "Third bibliographic catalogue of stellar radial velocities". Astronomy and Astrophysics Supplement. 108: 603–609. Bibcode:1994A&AS..108..603B.
- ^ Netopil, Martin; et al. (July 2017). "An investigation of the rotational properties of magnetic chemically peculiar stars". Monthly Notices of the Royal Astronomical Society. 468 (3): 2745–2756. arXiv:1703.05218. Bibcode:2017MNRAS.468.2745N. doi:10.1093/mnras/stx674.
- ^ Shulyak, D.; et al. (2014). "Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities". Monthly Notices of the Royal Astronomical Society. 443 (2): 1629. arXiv:1406.6093. Bibcode:2014MNRAS.443.1629S. doi:10.1093/mnras/stu1259. S2CID 96452769.
- ^ Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID 119108982
- "9 Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-27.
- Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. Vol. 2. Sky Publishing Corporation and the European Space Agency. p. 1009. ISBN 0-933346-83-2.
- ^ Mathys, G.; Lanz, T. (July 1997). "The variations of the BP star HD 137509". Astronomy and Astrophysics. 323: 881–885. Bibcode:1997A&A...323..881M.
- Cowley, A. P.; Houk, N. (August 1975). "An interesting new southern peculiar A star - HD 137509". Publications of the Astronomical Society of the Pacific. 87: 527–528. Bibcode:1975PASP...87..527C. doi:10.1086/129803.
- Kochukhov, O. (July 2006). "Remarkable non-dipolar magnetic field of the Bp star HD 137509". Astronomy and Astrophysics. 454 (1): 321–325. arXiv:astro-ph/0603831. Bibcode:2006A&A...454..321K. doi:10.1051/0004-6361:20064932. S2CID 17058487.
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